In this Phase II study the primary parameters are clinical and laboratory safety data and the plasma AUC and Cmax for T-20 when administered as a single dose and after steady state has been achieved. Viral RNA assays and the immunophenotyping panel results will be regarded as secondary endpoints. The investigational agent, T-20, is a 36-amino acid synthetic peptide. T-20 is a linear molecule composed of naturally-occurring I-amino acid residues. The results of nonclinical mechanism of action studies indicate that T-20 exhibits potent and selective inhibition of de novo infection and cell to cell virus transmission by binding to a critical region of gp41 which regulates the fusion of virus to host cell membranes. The investigational agent, T-20, is a 36-amino acid synthetic peptide. T-20 thus far has been studied in 16 HIV-1 positive volunteers in a Phase I multi-dose dose escalation study. Results indicate that no evidence of acute clinical or laboratory toxicity was associated with the administration of T-20. There was a dose-dependent antiretroviral effect of T-20 observed in this initial study.